An LED driver circuit often has a fixed output circuit topology, and its output terminal has a capacitor element. For example, a buck circuit topology has a simple wiring architecture and a low cost of an overall structure, and is widely applied in LED self-rectifying lamps. However, a LED driver circuit may have unusual situations including: 1. an abnormal short circuit of a power tube; and 2. an open output circuit (caused by abnormal conditions such as damage of an LED and disconnection of output lines, etc.). The abnormal situations may result in a large voltage at an output terminal, and hence result in the damage of an output terminal capacitor.